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daily-triage/linux-load-average-high-cpu-near-zero.md
Daily Triage Briefing

A Linux Host Shows High Load Average While CPU Utilisation Stays Near Zero

Impact Summary

A fictional Linux triage exercise in which a monitoring dashboard reports a high load average while CPU utilisation graphs remain almost flat, producing conflicting alerts that require careful evidence gathering before any remediation is attempted.

SeveritySEV-3
StatusResolved simulation
PlatformOperating Systems
Incident TypeOperating Systems
Published21 Aug 2026
Technologies Involved
Linux

Simulation Label

Fictional simulation. This exercise is a bounded, invented training scenario for practising operational reasoning. No real organisation, incident, telemetry, credentials or production identifiers are involved or implied.

Operational Summary

Root Cause

A recent verbose logging change filled the /var/log partition, saturating the underlying disk and blocking application worker processes in uninterruptible I/O wait, which raised load average without raising CPU utilisation.

Detection Method

Evidence-led guided investigation

Current Status

Resolved simulation

Affected Services

Linux

Incident Overview

At 09:14 on a fictional Monday, the monitoring platform for a mid-sized retail application fires two alerts within ninety seconds of each other for the same host, app-node-3. The first alert states Load Average Critical: 22.4 (1m).

The second alert, from a separate CPU utilisation check, states CPU Utilisation Normal: 6%. The on-call graduate administrator, Tomasz, is asked to triage the host before deciding whether to restart any services or escalate to the platform team.

The dashboards appear to disagree with each other, and Tomasz has thirty minutes before the next deployment window opens on an adjacent host.

Investigation Options

Review the available operational moves and select the best immediate action.

A

Immediately restart the application service on app-node-3 to clear the D-state processes

B

Collect and correlate uptime, mpstat, ps and iostat evidence before deciding on any remediation

C

Silence the load average alert as a false positive and continue monitoring CPU utilisation only

D

Immediately reduce the application's logging verbosity in production without reviewing current disk usage

Tags:Linux
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